Apparatus for treating fluids with ultrasounds

ABSTRACT

The present invention relates to a fluid processing apparatus for use in an elongate passage ( 10 ), the apparatus comprising one or more means for applying ultrasonic energy to fluid ( 16 ) within the passage ( 10 ) and means for constraining flow of fluid ( 30 ) towards the longitudinal axis of the elongate passage.

This invention is concerned with fluid processing devices, particularlybut not exclusively for use in the treatment of sewage. By the term“sewage” as used herein, we mean domestic/municipal and industrialwastewaters and sludges.

It has been found that the application of ultrasonic energy to sewageimproves subsequent response of the sewage to treatment. For example, inthe specification of European patent 0648531 there is described a fluidprocessing device comprising a chamber through which fluid to beprocessed may be fed, and an operating member having a circularcross-section in the chamber, the operating member comprising aplurality of surfaces including at least one interior circumferentialsurface, the device comprising means to cause said surfaces to vibrateat an ultrasonic frequency. In use, the fluid to be treated is flowedthrough the chamber and over the circumferential surface, wherebyultrasonic energy is provided to the flowing fluid.

It has been now found that an advantageous fluid processing a device,particularly for the treatment of raw sewage, comprises an elongatepassage conveniently of circular cross-section through which fluid to beprocessed is fed, a plurality of axially spaced operating members in thepassage, each operating member having an inner surface defining an innerpassage through which fluid flowing through the device passes, and meansto cause the inner surface of the operating members to vibrate atultrasonic frequency generally radially of the operating member. In use,sewage flow through the elongate passage flows through the innerpassages wherein it is subjected to ultrasonic energy derived from thevibrating inner surface of the operating members.

It has, however, been found that detritus contained in the raw sewage,such as rags, paper, plastics etc., tends to accumulate in areas of lowflow rate between the operating members, (ie. “dead” areas) which mayeventually produce a reduction to the rate of flow of fluid through, thedevice, and possibly cause a blockage. This problem is exacerbated in apreferred fluid processing device, wherein to increase the amount ofultrasonic energy applied to the fluid, the fluid also flows over outersurfaces of the operating members, particularly through generallyannular passages between said outer surfaces and the interior surfacedefining the elongate passage.

An object of the present invention is to overcome the problems of theprior art.

According to one aspect of the present invention there is provided afluid processing apparatus for use in an elongate passage, the apparatuscomprising:

-   -   one or more means for applying ultrasonic energy to fluid within        the passage;    -   wherein the apparatus further comprises means for constraining        flow of fluid towards the longitudinal axis of the elongate        passage.

In preferred embodiments the one or more means for applying ultrasonicenergy have an inner passage through which fluid flowing through theapparatus passes.

According to a further aspect of the present invention there is provideda fluid processing apparatus for use in an elongate passage, the fluidprocessing apparatus comprising:

-   -   one or more means for applying ultrasonic energy to fluid within        the passage, the means for applying ultrasonic energy comprising        a vibration member having an inner passage;    -   fluid directing means for directing fluid to flow towards the        inner passage.

By constraining or directing the fluid flow towards the longitudinalaxis of the elongate passage or towards the inner passage, an increasein the flow rate of the sewage is produced. By this means a greaterproportion of solids contained in the sewage will flow through thedevice on or more closely adjacent to the longitudinal axis or directlythrough the inner passage and thus flow through areas of higherultrasonic density than otherwise would be the case.

Additionally by increasing the fluid velocity, cavitation is producedwhich allows the creation of ultrasonic vibrations in those section ofthe passage which are located between adjacent operating members,increasing the efficiency of the device.

In addition, the increased velocity of flow along the passage ensuresthat a majority of detritus flows directly through the passage: anydetritus which has flowed from the axis or the inner passage will bepulled by the venturi effect towards the longitudinal axis or innerpassage.

In this manner it has been found that tendency for detritus toaccumulate in the areas of low flow rate between adjacent operatingmembers is reduced.

Additionally, by increasing the proportion of detritus which flowsgenerally along the longitudinal axis directly through the device,reduction to the flow of fluid over the outer surfaces of the operatingmembers by the accumulation in the space between said outer surfaces andthe walls defining the elongate passage is minimised.

The means for constraining flow of fluid or the fluid directing meanscan be produced separately from the elongate passage and, therefore, canbe mounted in existing elongate passages.

Preferably said means for constraining flow of fluid or the fluiddirecting means comprises a funnelling device through which fluid to betreated flows into the device.

The funnelling device can be produced from a sheet of material which isnot corrosive in the fluid, for example, stainless steel or plasticsmaterials.

Conveniently said funnelling device is operative to reduce thecross-sectional area through which fluid flows by at least a factor of4. In preferred embodiments said funnelling device is operative toreduce the cross-sectional area through which fluid flows by at least afactor of 8.

Thus where the elongate passage is of circular cross-section, having adiameter of 150 mm, the funnel device may, reduce the cross-sectionalarea of the passage to approximately 50 mm diameter.

Preferably said elongates passage as of circular cross-section. Thepassage, therefore has no corners where detritus may build up.

Conveniently the funnelling device is located within the elongatepassage upstream of the one or more means for applying ultrasonicenergy. Accordingly, the fluid flow is constrained before it reaches themeans for applying ultrasonic energy.

Preferably the longitudinal axis of the inner passage of the or eachmeans for applying ultrasonic energy is substantially coincident withthe longitudinal axis of the elongate passage.

Conveniently there are provided a plurality of means for applyingultrasonic energy.

The more means for applying ultrasonic energy that are present thelarger the proportion of fluids which will be treated.

Preferably there are provided at least four means for applyingultrasonic energy. By so constraining the flow of fluid being treatedtowards the longitudinal axis of the elongate passage, it has been foundthat good flow characteristics of the fluid through a significantlylarger number of sequential operating members has been possible, thanwould otherwise have been the case. In particular, it has been found bythis method that five or more operating devices may be contained withinthe same elongate passage, enabling a highly efficacious treatment ofthe fluid to be obtained over a relatively compact distance.

In preferred embodiments each means for applying ultrasonic energycomprises a operating member connected to the vibration member, theoperating member being connected to a source of ultrasonic energy.

Preferably an inner surface of the inner passage is arranged to vibrateradially.

According to a yet further embodiment of the present invention there isprovided a method of treating fluids, the method comprising: placing thefluid processing apparatus of any, preceding claim into an elongatepassage and passing the fluid through the elongate passage.

Preferably the fluid is sewage sludge.

The invention will now be described, by way of illustration only, withreference to the following example and the accompanying figures.

In the accompanying figures:

FIG. 1 is a schematic view illustrating part of a flow circuit in whichthe fluid processing device which is a preferred embodiment of thisinvention is installed;

FIG. 2 is a sectional view-showing the mounting of the longitudinalmember, of a means to apply ultrasonic energy;

FIG. 3 is a side view of the fluid processing device which is apreferred embodiment of this invention;

FIG. 4 is an enlarged view showing the mounting of the ultrasonic deviceto than elongate member; and

FIG. 5 is an enlarged view of a funnel member of a preferred embodiment.

The fluid processing device which is a preferred embodiment of thisinvention is specifically for use in the treatment of raw sewage, and isadapted to be located in a flow-line 5 affording a branch to a mainflow-line 4, flow of fluid therethrough being controlled by valves V1,V2, V3 and V4 (see FIG. 1). A preferred embodiment, comprises alongitudinal member afforded by a pipe 10 of circular cross-section,through which in use raw sewage is fed.

Mounted on the longitudinal member 10 are a plurality, in this examplefive, of operating devices 12, each operating device 12 comprising anoperating member 14, and an ultrasonic device 16 connected thereto. Eachultrasonic device 16 comprises a transducer 24, and a flanged booster 26and a extender 28.

The operating member 14 is of substantially annular cross-section,comprising an outer surface 18, and an inner surface 20. Provided-on theoperating member 14 is a tangential flat 22, to which the extender 28 ofthe ultrasonic device 16 is secured conveniently by means of a weld, theultrasonic device passing through the wall of the pipe 10.Alternatively, the extender 28 and the operating member 14 can besecured by a screw.

In the present example there are five operating devices 12 mounted onthe pipe 10. However, any required number of operating devices can bepresent.

The inner surface 20 of each operating member defines an inner passageof circular cross-section through which fluid flowing through the devicepasses, and additionally the annular space between the outer surface 18of the operating member 14 and the inner wall 11 of the pipe 10 providesan outer passage 19 through which fluid may also flow.

In use, the ultrasonic devices 16 are each energised, causinglongitudinal vibrations at ultrasonic frequency to be applied from theextender 28 to the flat face of its attachment to the operating member14. Specifically, the operating member 14 has an internal radius R1 andan external radius R2, the relationship being such that (R1+R2)/2=Kλ,where K is an integer, and λ is the wavelength of the vibrations appliedby the ultrasonic device to the operating member 14. In thisconfiguration the outer surface 18 and the inner surface 20 of theoperating member alternatively radially expand and contract in apulsating manner at ultrasonic frequency, apply ultrasonic energy tofluid flowing through the pipe 10.

Mounted in the upstream end of the pipe 10 is a funnel device 30 (FIG.4) which is a sliding fit in the end of the pipe 10, flanges 32 beingprovided to locate the funnel member 30 in a desired location within thepipe. The funnel has a frusto-conical surface 34 which reduces theeffective radius of pipe 10 typically from substantially 75 mm tosubstantially 25 mm, ie. approximately equal to the radius R1, reducingthe cross-sectional area of the flow passage through the device by afactor of 8 to 10.

In this manner fluid fed through the device is constrained towards thelongitudinal axis of the device, increasing the flow rate, and ensuringa greater proportion of solids are located on or close to thelongitudinal axis. Additionally, the higher flow rate increasescavitation within the fluid flow, and, therefore, effective ultrasonicvibrations will occur in the sections of the elongate passage locatedbetween adjacent operating members. Further, since the fluid is flowingat a higher velocity through the device than would otherwise be thecase, the majority of detritus flows directly through the internal flowpassage defined by the interior surfaces 20 of operating members 14. Inthis way the flow of detritus into the relatively “dead” spaces betweenadjacent operating members 14 is reduced, reducing the tendency of suchdetritus to clog the outer passage 19.

Further, such detritus as may flow from the longitudinal axis will tendto be pulled back into the main flow stream by the venturi effect of therelatively high speed flow of the fluid through the device.

In this way it has been found that a high density of ultrasonic devicesmay be utilised, applying a large amount of ultrasonic energy to thefluid flow through the device over a relatively short longitudinaldistance, with significantly reduced tendency for blockage to occur.

It is to be appreciated that whilst this invention has been devisedspecifically for the treatment of raw sewage, the invention may beutilised in the treatment of other fluids, where similar or analogousproblems arise, and in particular where it is desired to applyultrasonic energy to the fluid in an efficient manner.

It will be understood that the embodiment illustrated shows oneapplication of the invention only for the purposes of illustration. Inpractice the invention may be applied to many different configurations,the detailed embodiments being straightforward for those skilled in theart to implement.

The means for applying ultrasonic energy can be of any shape, forexample with a rectangular cross-section. There need not be an innerpassage provided therein.

The funnelling device call be integral with the pipe.

The funnelling device may be formed such that there is provided an innerpassage with a frusto-conical surface. The outer surface of the devicecould be any desired shape.

There may be any suitable number of ultrasonic devices placed in theelongate passage for example, 4, 5, 6, 7, 8, 9, 15, 20.

1. Fluid processing apparatus for use in an elongate passage, the fluid processing apparatus comprising: one or more means for applying ultrasonic energy to fluid introduced into the elongate passage, the means for applying ultrasonic energy comprising an operating member having an inner passage through which said fluid can flow, the operating member being provided within the elongate passage such that an outer passage is formed between an inner surface of the elongate passage and an outer surface of the operating member; wherein said outer passage is in fluid communication with the inner passage within the elongate passage, and flow constraining means in the form of a tapering funnel is provided in said elongate passage upstream of, and spaced from, the inner passage, for introducing said fluid into the elongate passage and for directing said flow of said fluid towards the inner passage.
 2. Apparatus according to claim 1, wherein said tapering funnel is operative to reduce a cross-sectional area through which fluid flows by at least a factor of
 4. 3. Apparatus according to claim 2, wherein said tapering funnel is operative to reduce the cross-sectional area through which fluid flows by at least a factor of
 8. 4. Apparatus according to claim 1, wherein said elongate passage is of circular cross-section.
 5. Apparatus according to claim 1, wherein a longitudinal axis of the inner passage of the or each means for applying ultrasonic energy is substantially coincident with a longitudinal axis of the elongate passage.
 6. Apparatus according to claim 1, wherein there are provided a plurality of means for applying ultrasonic energy.
 7. Apparatus according to claim 1, wherein there are provided four means for applying ultrasonic energy.
 8. Apparatus according to claim 1, wherein the or each means for applying ultrasonic energy comprises the operating member being connected to a source of ultrasonic energy.
 9. Apparatus according to claim 1, wherein an inner surface of the inner passage is arranged to vibrate radially.
 10. A method of treating fluids, the method comprising; placing the fluid processing apparatus of claim 1 into an elongate passage and passing the fluid through the elongate passage.
 11. A method according to claim 10 wherein the fluid is sewage sludge.
 12. Apparatus according to claim 1, wherein the or each vibration member is a substantially annular member with an internal radius R1 and an external radius R2.
 13. Apparatus according to claim 12, wherein the or each vibration member satisfies the relationship (R1+R2/2=Kλ) where K is an integer and λ is the wavelength of the vibrations applied to the vibration member.
 14. Apparatus according to claim 12, wherein the outer passage comprises an annular space. 